Reduced noise diffuser for a motor-fan assembly

ABSTRACT

An air diffuser for a motor-fan unit having reduced blade passage frequencies, and reduced noise generation, includes a baffle plate, external vanes, internal vanes, diffuser ports, and a central opening. The baffle plate of the diffuser is made integral with the internal and external vanes, such that any leaking, rattling, or pure tone noise that may be generated from air movement over the surface of the diffuser are prevented or reduced. Additionally, the number of internal and external vanes provided by the diffuser is that equal to a prime number, thus resulting in a reduction of harmonic and pure tone noise generated during the operation of the motor-fan unit.

TECHNICAL FIELD

The present invention generally relates to diffusers used in association with various motor-fan systems. More particularly, the present invention relates to an air diffuser that reduces vane passage frequencies, and associated noise, which is generated from air movement over the surface of the diffuser. Specifically, the present invention is directed to a noise reducing diffuser that operatively secures the brushes of an electric motor. More specifically, the present invention relates to a noise reducing diffuser that is interchangeable with existing diffusers installed in various motor-fan units.

BACKGROUND OF THE INVENTION

Electric motors are well known in the art and have been put to use in a variety of applications, including the handling of air. In this circumstance, an electric motor is coupled to a fan, creating a motor-fan unit, which produces an airflow as needed. When providing air movement, the motor-fan unit may supply cooling air to the motor, so as to maintain the motor's operating temperature at an optimal level, allowing the motor's operating life to be extended. The motor-fan unit may also be used to generate working air for vacuum type devices.

To achieve this effect, the fan is mounted on a motor driven shaft, which draws air into a fan shroud. The fan shroud compresses or pressurizes the incoming air, which is resultantly released into the motor housing via one or more ports in a diffuser plate, causing the air to be directed toward the motor windings. As a result, the heat from the motor is drawn into the airflow and exhausted from the motor housing, thus enhancing the motor's operating life.

Many diffusers used with motor-fan units, incorporate radial turning vanes with a separately attached baffle plate to move the pressurized air from the fan shroud to the motor assembly. However, the baffle plates of these diffusers are not made integral with the turning vanes. This results in a baffle plate that does not form a complete seal with the attached turning vanes. Because of this inadequate or compromised seal, the diffuser generates leaking, rattling, and pure tone noises as the motor-fan unit draws air through the diffuser. In addition, blade passage frequencies are also created as air is passed over the diffuser's vanes. As such, many motor-fan units are uncomfortably noisy to many users. Further, the use of such motor-fan units may be limited to those applications where such noise can be tolerated.

In addition to the diffuser portion of the motor-fan unit, the motor itself comprises field windings that surround an armature that is centrally located on a shaft, which is rotatably mounted on suitable bearings. A commutator is also mounted on the shaft and placed in electrical contact with a power supply by a pair of opposed brushes contacting the commutator. Typically, these brushes and/or armature are completely or partially closed off from the cooling air provided by the fan unit. As such, the motor's efficiency and operating life are reduced due to the heat generated by the motor.

Therefore, there is a need for a diffuser for a motor-fan unit with radial turning vanes that has an integrated baffle plate to provide reduced noise during the motor-fan unit's operation. Additionally, there is a need for a reduced noise diffuser that allows cooling air to pass to the brushes and/or armature of the motor while supporting the brushes of the motor. Further, there is a need for an interchangeable diffuser with reduced vane passage frequencies, and reduced noise generation that can be used in association with existing motor-fan assemblies, while providing suitable cooling for the motor's armature and/or brushes.

DISCLOSURE OF INVENTION

In light of the foregoing, it is a first aspect of the present invention to provide a reduced noise diffuser for a motor-fan assembly.

It is another aspect of the present invention to provide a diffuser interposed between a shrouded fan assembly and a motor assembly having a shaft that rotates a fan carried within the shrouded fan assembly, the diffuser comprising a baffle plate having a motor side and a fan side, the baffle plate having an opening therethrough; and a plurality of vanes extending from the motor side, each vane having an external portion which radially extends from the baffle plate, wherein adjacent vanes have a port therebetween, the plurality of vanes directing air flow generated by the fan from the fan side through the ports to the motor side.

It is yet another aspect of the present invention to provide a motor-fan assembly comprising a field winding; an armature having a shaft, the armature rotatably mounted within the field winding; a fan attached to the shaft; and a diffuser interposed between the fan and the field winding, the diffuser comprising a baffle plate having a motor side and a fan side; the baffle plate having an opening therethrough; a plurality of vanes extending from the motor side; each vane having an external portion which radially extends from the baffle plate wherein adjacent vanes have a port therebetween; and the plurality of vanes directing airflow generated by the fan from the fan side through the ports to the motor side.

DESCRIPTION OF THE DRAWINGS

These and other features and advantages of the present invention will become better understood with regard to the following description, appended claims, and accompanying drawings where:

FIG. 1 is a partially sectioned front elevational view of a motor-fan unit according to the present invention showing the details of a motor assembly, an end plate assembly, a diffuser assembly, and a fan assembly;

FIG. 2 is an exploded perspective top view of the motor-fan unit according to the present invention depicting details of the motor assembly, the end plate assembly, the diffuser assembly, and the fan assembly;

FIG. 3 is an exploded perspective bottom view of the motor-fan unit according to the present invention depicting details of the motor assembly, the end plate assembly, the diffuser assembly, and the fan assembly;

FIG. 4 is a plan view of the end plate assembly depicting details of a motor-side of the end plate;

FIG. 5 is an elevational view of the end plate assembly depicting further details of the end plate assembly, including a brush retainer assembly and motor brackets;

FIG. 6 is a partially sectioned side elevational view of the end plate assembly depicting details of a commutator receiver;

FIG. 7 is a perspective view of the end plate assembly depicting further details of the motor-side thereof, including the location of brush retainers adjacent the commutator receiver;

FIG. 8 is an enlarged partially sectioned side elevational view as seen along line 8-8 in FIG. 4, depicting details of the brush retainer according to the present invention;

FIG. 9 is a plan view of the end plate according to the present invention depicting details of the diffuser side of the end plate assembly;

FIG. 10 is a perspective view of a fan side of the diffuser assembly according to the present invention;

FIG. 11 is a plan view of the diffuser assembly including a baffle plate, a plurality of external vanes, and a plurality of diffuser ports;

FIG. 12 is a perspective view of a motor side of the diffuser assembly according to the present invention;

FIG. 13 is a perspective view of a diffuser assembly according to the present invention depicting brush cap assemblies extending from the surface of the diffuser assembly;

FIG. 14 is a plan view of a diffuser assembly according to the present invention showing the pair of brush cap assemblies located adjacent a central opening of the diffuser;

FIG. 15 is a front sectional view along line 15-15 in FIG. 14 of the diffuser assembly according to the present invention depicting the brush cap assemblies extending axially inward to protrude beyond the radial channel members located on the diffuser;

FIG. 16 is a side sectional view along line 16-16 in FIG. 14 of the diffuser assembly according to the present invention depicting details of the brush cap assemblies, including a channel formed within each cap assembly to direct air toward the brushes in the motor-fan unit;

FIG. 17 is a perspective view of the diffuser according to the present invention enlarged to show details of an alternative brush cap assembly having snap-lock projections located thereon to effect attachment of the end cap assembly to the diffuser assembly; and

FIG. 18 is an enlarged perspective view of an end plate and diffuser according to the present invention having an alternative brush cap assemblies with snap lock projections that engage surfaces on the commutator receiver of the end plate to couple the end plate to the diffuser.

BEST MODE FOR CARRYING OUT THE INVENTION

A motor-fan unit, indicated generally by the numeral 10 in the accompanying FIGS. 1-3, generally includes a motor assembly 12 and a fan assembly 14. The motor assembly 12 comprises a lamination stack 16, an armature 18, field windings 19, a commutator 20, and brushes 22 (best seen in FIG. 7). A shaft 24 with a mounted armature 18 is supported by suitable bearings 26, such that the shaft 24 rotates when the motor assembly is energized. The commutator 20 allows the shaft 24 to rotate while allowing the armature 18 to remain electrically connected with a power supply (not shown) via the brushes 22.

As shown in FIG. 1, the motor assembly 12 is configured with the commutator 20 proximate the fan assembly 14. The fan assembly 14 of the motor-fan unit 10, comprises a fan 28 coupled to an end 30 of the shaft 24 that is proximate the commutator 20, via a nut 32. However, any other type of suitable system for connecting the fan 28 to the shaft 24 may be utilized. Covering the outside of the fan assembly 14 is a shroud 34. The shroud 34 has a cover portion 38 which has a centrally positioned intake port 36 that is coaxially located with axis A of shaft 24. The intake port 36 allows the fan assembly 14 to draw air into the shroud 34 where it is pressurized or compressed and radially exhausted. The air may then be directed through the motor assembly.

The motor assembly 12 is provided with an end plate assembly which is generally indicated by the numeral 42 shown in FIGS. 1-9. The end plate assembly 42, shown clearly in FIGS. 2 and 3, generally includes a planar plate portion 44, which may be annular as shown, and a motor bracket portion 46 that extends from the plate portion 44 toward the motor 16. The motor bracket portion 46, shown more clearly in FIGS. 4 and 5, is adapted to allow the motor assembly 12 to be rigidly mounted or fixated to the end plate assembly 42. Continuing with FIGS. 3 and 4, the end plate assembly 42 defines a central opening 47, which receives the end of the motor's shaft 24 that is proximate the commutator 20. The end plate assembly 42 may be provided with a commutator receiver, generally indicated by the numeral 48 that receives the commutator 20 and provides suitable clearance for the free rotation of the commutator 20. The commutator receiver 48 shown clearly in FIGS. 5 and 6 may bulge axially outwardly of planar plate portion 44 to define a well 50, in which at least a portion of the commutator 20 resides. The well 50 may also retain a bearing 26 which is used to support the shaft 24, thereby allowing the shaft 24 to freely rotate. In addition, the commutator receiver 48 may include a plurality of stepped concentric recesses 52, 54, 56 that accommodate the profile of both the commutator 20 and the bearing 26. This arrangement allows the commutator 20 to be placed close to the fan assembly 14, such that the commutator 20 can receive cooling air prior to the air's passage over the motor's armature 18. As a result, the commutator 20 is more efficiently cooled, and the performance of the motor is enhanced. Returning to FIGS. 2 and 3, it is shown that in order to secure the motor assembly 12 to the end plate 42, a fastening plate 58 is used. The fastening plate 58 has tabs 60 with holes therethrough for receiving fasteners that are secured into a receiver 61 carried by each motor bracket portion 46.

Because the brushes 22 make electrical contact with the commutator 20 during the operation of the motor-fan unit 10, a pair of brush retainers generally indicated by the 5 numeral 62 are provided by the end plate assembly 42. The structure of each brush retainer 62 is largely identical to the other, with one brush retainer 62 being a mirror image of the other. Therefore, the following discussion will describe only a single brush retainer 62. As shown in FIGS. 4-8, and more clearly seen in FIGS. 6-8, the brush retainer 62 may be in the form of a channel-like member having three contiguous walls or members 64, 66, and 68 that define an open end 70, such that the three contiguous walls or members 64, 66, 68 serve to cradle the brush 22. It is also contemplated that the brush retainer 62 protrudes toward the motor assembly 12 to facilitate the manufacture thereof.

As shown in FIG. 9, the brush retainers 62 each contain an open mouth 72, which is contiguous with the open end 70, and which opens toward the fan assembly 14. A projection in a mold cavity may be used to create the open mouth 72 of the brush retainer 62 during fabrication. Thus, by using the open mouth 72, mold design is greatly simplified, and the use of sacrificial molding or subsequent machining to create tubular brush retainers as used in the art is obviated. Further, the formation of an open, resilient-type brush retainer 62 allows for interference fitting of the brush 22 within the brush retainer 62. As a result of this interference fit, the use of retaining clips, which are commonly used when attaching the brush 22 to a motor housing, are eliminated. The brush retainer 62, may be formed as a single piece or may contain spaced portions to suitably support the brush 22. As an alternative to the channel-like brush retainer 62 shown in the Figs., it is also contemplated that the brush retainer 62 may include an L-shaped member or may incorporate one or more posts to locate the position of the brush 22.

Continuing with the brush retainer 62 as shown in FIGS. 7 and 8, the brush retainer 62 includes a wall or member 64 that extends axially outward from the plate portion 44 toward the motor assembly 12, a wall or member 66 that extends outwardly from and generally at a right angle to the wall or member 64, and a wall or member 68 extending axially toward the plate portion 44 from the wall or member 66. The wall or member 66 is axially spaced from the end plate 42 to define a suitable vertical clearance 74 for the brush 22, while the wall or members 68 and 64 serve to define a horizontal clearance 76. As previously discussed, the wall or members 64, 66, and 68 may be spaced such that clearances 74 and 76 create an interference fit between the brush 22 and the brush retainer 62. It should also be appreciated that the wall or member 68 may not make a complete connection with the plate portion 44. Thus, a gap or notch 78 is created between the plate portion 44 and the wall or member 68 along one side of the brush retainer 62, as shown. A support member 80, such as a post, may extend axially from the plate portion 36 to support the cantilevered members 66 and 68. The support member 80 is placed adjacent the brush retainer 62 near an edge 82 of the brush retainer 62 that is closest to the commutator receiver 48. At this location, the support member 80 may further aid the brush retainer 62 in maintaining the position of the brush 22.

To ensure contact between the brush 22 and the commutator 20 of the motor 16, the brush 22 is biased into engagement with the commutator 20, as shown in FIG. 7. The biasing action is performed by a spring 84 mounted on a spring holder 86 that is provided by the end plate assembly 42. Although a spring is typically used, other systems for biasing the brushes are contemplated. Specifically, the spring 84 includes a coil 88, a leg 90, and a leg 92 which are employed to bias the brush 22 toward the commutator 20. The coil 88 is press fit over the spring holder 86, and the leg 90 is fixed in place with a suitable clip, such as spring retainer projection 94 that is formed on the plate portion 44.

While spring retainer projection 94 may comprise a wall, an L-shaped projection may be used as shown in FIG. 7. Thus, the torsional force generated by the spring 84 holds leg 90 against spring retaining projection 94, thus preventing leg 90 from moving axially beyond spring retaining projection 94. Leg 92 of the spring 84 is positioned so that it contacts the rear of the brush 22, and causes the brush 22 to be urged toward the commutator 20. Since the brush 22 may be inserted after the assembly of the motor assembly 12, it may be necessary to preload the spring 84 to temporarily hold it in place. To assist in the preloading of the spring 84, a spring retaining projection 96 may be provided on the surface of the end plate assembly 42 or the brush retainer 62. The spring retaining projection 96 is located so that when the leg 92 of the spring 84 is compressed, a torsional force is created within the spring 60 sufficient to hold leg 92 against the spring retaining projection 96. Specifically, in the embodiment shown in FIG. 7, an L-shaped spring retaining projection 96 extends axially inward from member 66 of the brush retainer 62, thereby defining a spring recess 98 in which an end 100 of leg 92 may be inserted to allow the spring 84 to assume a preloaded condition as shown in FIG. 4. Prior to placing the brush 22 within the brush retainer 62, leg 92 is compressed so that it clears the brush retainer 62 and any extending portion of the brush 22. Once the brush is inserted within the brush retainer 62, the leg 92 is placed in contact with the rear of brush 22 to urge the brush 22 toward the commutator 20.

As shown in FIG. 9, the brush retainers 62 define an open mouth 72 within the end plate assembly 42, which open toward the fan assembly 14 and extend into a portion of the commutator receiver 48. The opening of the mouth 72, allows cooling air from the fan assembly 14 to flow past the brushes 22, and motor 16 as will be described more completely below. To allow air to pass over the armature 18, or other parts of the motor assembly 12, the end plate assembly 42 provides a pair of cavities 104. These cavities 104 may be at least partially sealed from the mouth 72, to prevent particulates generated from the brushes 22 from being carried downstream into the other areas of the motor assembly 12. To further limit the passage of particulates into the motor assembly 12, dividers 106 and 108 extend from the plate assembly 42. To further limit particulates from entering the motor assembly 12, a bead of sealant may be provided, which extends adjacent cavities 104, and between the cavities 104 and each mouth 72 of the brush retainer 62. As shown, the dividers 106, 108 generally cordon off a sector surrounding each of the mouths 72, such that the plate portion 44 is separated into distinct regions.

Air drawn into the shroud 34 by the fan assembly 14, is directed to the motor 16 by a diffuser assembly that is designated generally by the numeral 120. The diffuser assembly 120 is interposed between the fan 28 and the end plate assembly 42 and is configured to be interchangeable with existing diffuser assemblies that are part of other motor-fan units 10. That is, the diffuser assembly 120 of the present invention is designed to cooperate with end plate assemblies 42 of varying motor-fan units 10 so that the brushes 22 of such unit 10 are sufficiently supported. As shown in FIGS. 10-16, the diffuser assembly 120 includes a baffle plate 122 which provides a fan side 123 which is opposite a motor side 124. The fan side 123 is positioned adjacent the fan assembly 14 when the motor-fan unit 10 is assembled. Likewise, the motor side 124 is positioned adjacent the end plate assembly 42 and the motor assembly 12 when the unit 10 is assembled. The baffle plate 122 includes an outer edge 125 which joins the fan side 123 to the motor side 124 and the plate also provides a central opening 126 extending therethrough. The central opening 126 receives and seats the commutator receiver 48 to allow contact between the commutator 20 and the brushes 22. Extending from the motor side 124 are a plurality of curvilinear vanes designated generally by the numeral 128. The vanes 128 are spaced apart and each vane has a plate edge 129 connected to the motor side and a ring edge 130 opposite the plate edge. The curvilinear vanes 128 are disposed about the outer periphery of the motor side 124. In particular, each vane 128 provides an external portion 131 that extends radially outwardly from the outer edge 125 on the motor side 124 and an internal portion 132 that extends from the motor side 124. The adjacent vanes 124 form a port 134 therebetween. A vane support ring 135 connects the external portions of the curvilinear vanes to one another and, in particular, joins the respective ring edges 130 of each vane 128. The ring 135 has an inner diameter edge 136 and an outer diameter edge 137. It will be appreciated that the inner edge 136 has a diameter equal to or somewhat greater than the diameter of the outer edge 125. The internal portions 132 of the curvilinear vanes 128 collectively form a collection chamber designated generally by the numeral 138. The construction of the baffle plate 122 is ideally suited for a molded construction, but it will be appreciated that other materials could be used in formation thereof. Accordingly, the curvilinear vanes 128 are integral with the baffle plate 122 and the vane support ring 135 to provide a sturdy and easily manufactured construction.

The curvilinear vanes 128 may comprise radial turning vanes, wherein the number of vanes is equal to that of a prime number. It is believed that by having such an arrangement, the diffuser assembly 120 is able to reduce the harmonic interaction between the fan 14 and the diffuser at certain revolutions-per-minute multiples as the fan assembly 14 rotates. In general, many harmonics may be generated by air passing by over the surface of the diffuser vanes. For example, in arrangements where a diffuser utilizes a number of vanes not equal to a prime number, generated harmonics may occur at multiples of the smallest mathematical factor for the number of vanes present. In contrast, a diffuser having a number of vanes equal to that of a prime number only has two factors (i.e. the number 1 and the prime number itself). As such, the use of the diffuser 128 with a number of vanes equal to that of a prime number eliminates the factor harmonics that would otherwise be created by a diffuser with a number of vanes not equal to a prime number.

When the unit 10 is assembled and the motor assembly 12 rotates the fan assembly 14, air is drawn in through the shroud intake 34 and into the fan assembly 14. The fan assembly 14 exhausts the air radially such that it swirls around within the interior of the shroud and is redirected by the baffle plate 122 and, in particular, the curvilinear vanes 128. The air is guided through the ports 134 and swirls about the collection chamber 138 so that the air is forced radially inwardly toward the central opening 126 where it is then redirected so as to flow through the cavities 104 and other regions of the end plate assembly 42. Accordingly, the air drawn in through the shroud intake 136 is directed through the motor assembly 12 as needed for the end application.

Specifically, the vanes 128 may comprise radial turning vanes and/or may be equal in number to that of a prime number. For example, the number of turning vanes 128 may total 23, 29, or 37, although any other suitable prime number of turning vanes 128 may be utilized. By having such an arrangement, the diffuser assembly 120 is able to reduce the harmonic interaction between the fan 14 and the diffuser 120 at certain rpm multiples as the motor-fan unit 10 is in operation. More specifically, as high velocity air departs from a vane the resulting airflow also includes a vortex component that shears against other nearby vanes resulting in noise. The generated noise has its largest magnitude at frequencies equal to the multiples of the fan revolutions per minute (rpm) and the number of diffuser vanes. Thus, by altering the number of vanes 128 and/or the rpm of the fan 28 of the motor-fan unit 10, the noise frequencies with higher magnitudes may be shifted to different frequencies, thus minimizing the noise that would otherwise occur. As such, the noise generated by air passing through the diffuser 120 is thereby reduced.

Additionally as shown in FIGS. 12-16, the diffuser assembly 120 contains one or more brush cap assemblies 139. The brush cap assemblies 139 may be made integral with the baffle plate 122 during manufacturing of the diffuser 120, or may be connected to the baffle plate 122 using known techniques, including but not limited to thermal welding, adhesives, or screw-type connection. The brush cap assemblies 139 are configured to coact with the brush retainer 62 to trap the brushes 22 therebetween. In general, the brush cap assemblies 139 provide a surface that substantially closes the open mouth 72 of the brush retainer 62 located on the end plate assembly 42. To contact the brushes 22, or otherwise penetrate the opening of the mouth 72, the brush caps 139, taking on the form of a projection, may extend axially toward the motor assembly 12, beyond the vanes 128 to a desired extent. In one arrangement, the brush cap assembly 139 will not extend such that its contact with the brushes 22 would interfere with the proper assembly of the motor-fan unit 10. The brush cap assembly 139 generally conforms to the contours of the mouth 72 of the brush retainer 62, and may be toleranced to provide a clearance that would allow dust or particulates from the brushes 22 to escape through open end 70 of the brush retainers 62. By providing such clearance, dust build-up on the brushes 22 is reduced, and the airflow generated by the motor-fan unit 10 is able to pass over and cool the brush 22, thereby extending the life of the brush 22 and the motor 16. Further, the air escaping the brush retainer 62, at the radial interior extreme of the brush retainer 62 at the open end 70 facing the commutator 20, flows over the commutator 20, keeping it cooled.

As shown in FIGS. 12-18, the brush cap assemblies 139 have a generally rectangular shape to conform to the rectangular opening of the open mouths 72 of the end plate assembly 42. To channel air from the fan assembly 14 toward the brushes 22, the brush cap assemblies 139 may be provided with channels 140. The channels 140 are formed between upstanding members 142 and 144 that are positioned on the motor side 124 of the diffuser 120. Members 142, 144 are generally located adjacent the diffuser central opening 126 and may radially project to an extent into the opening. To accommodate the extension of the brush cap members 142,144 into the region of the commutator receiver 48, recess window 146 may be formed on the commutator receiver 48, as shown clearly in FIG. 7. Advantageously, an interference or friction fit between the members 142,144 and the commutator receiver 48 may be used in coupling the end plate assembly 42 and the diffuser assembly 120 together.

Upstanding members 142 and 144 are of a suitable height to the internal curvilinear vanes 128 to allow for proper attachment of the diffuser assembly 120 to the end plate assembly 42. Further, upstanding members 142,144 may extend sufficiently beyond the height of the vanes 128 to an extent, such that they extend into the open mouths 72 defined by brush retainers 62. As a result the diffuser 120 is capable of attachment to the end plate assembly 42. Upstanding member 142 may have a raised edge 148 sized to fill the gap or notch 78 between the plate portion 44 and member 68 of the brush retainer 62. In this way, the brush cap assembly 139 encloses the brushes 22 when the end plate 42 and diffuser 120 are coupled to one another. Adjacent the raised edge 148, upstanding member 142 may be provided with a landing 150, which has the same height as upstanding member 144, thereby forming a recessed area that lies adjacent to the brush 22 when the diffuser assembly 120 and end plate assembly 42 are joined. The channel 140, opens toward the motor assembly 12 between the landing 150 and upstanding member 144. This arrangement, allows air generated by the fan assembly 14 to be distributed across the exposed surface 152 of the brush 22 that lies adjacent the brush cap assemblies 139 shown in FIG. 7. The air directed through the channels 140 allows heat from the brushes 22 to be carried away, thus improving operation of the motor 16.

An alternative embodiment of the brush cap assemblies 139 are shown in FIGS. 17 and 18, which may be used in coupling the diffuser 120 to the end plate assembly 42. To supplement the interference or friction fit between brush cap assembly 139 and the walls of open mouth 70 or surfaces of commutator receiver 48, the brush cap assembly 139 may be provided with a projecting surface, generally indicated by the numeral 154, that performs a snap-lock function in connection with an attachment surface 156 provided by the recess window 146 of the end plate assembly 42. It will be appreciated that projecting surface 154 may be one of a number of configurations commonly used in the art to perform a snap-lock function, including but not limited to a flexible tab, a rounded surface, or a tapered leading surface 158 and stop surface 160 combination as shown in FIG. 17.

As shown in FIGS. 17 and 18, brush cap assemblies 139 may have triangular projections 162 extending radially inward from each member 142,144. The tapered surface 158 of projection 162 slopes outwardly from a member 142 or 144 toward diffuser 80. A stop surface 160 extends inwardly from the tapered surface 158 and is located vertically on members 142,144 to provide a clearance at 164 for the receipt of a portion of the commutator receiver 40. When attaching the diffuser 120 to the end plate 42, the tapered surface 158 causes gradual deflection of members 142,144 and/or the members 64,66,68 of the commutator receiver 40. Once the brush cap assemblies 139 are fully inserted within the open mouths 72 of the brush retainers 62, the stop surface 160 engages the attachment surface 156, such that end plate assembly 42 and diffuser 120 are coupled together.

It will, therefore, be appreciated that one advantage of one or more embodiments of the present invention is that the noise and vane passage frequencies associated with air movement over the diffuser's vanes are reduced. Still another advantage of the present invention is that the diffuser plate is configured, such that, the diffuser is capable of replacing a previously installed diffuser of an existing motor-fan unit. Yet another advantages of the present invention is that the diffuser is able to support the brushes of the motor-fan unit without additional adjustment to the diffuser.

Although the present invention has been described in considerable detail with reference to certain embodiments, other embodiments are possible. Therefore, the spirit and scope of the appended claims should not be limited to the description of the embodiments contained herein. 

1. A diffuser interposed between a shrouded fan assembly and a motor assembly having a shaft that rotates a fan carried within said shrouded fan assembly, the diffuser comprising: a baffle plate having a motor side and a fan side, said baffle plate having an opening therethrough; and a plurality of vanes extending from said motor side, each said vane having an external portion which radially extends from said baffle plate, wherein adjacent vanes have a port therebetween, said plurality of vanes directing airflow generated by the fan from said fan side through said ports to said motor side.
 2. The diffuser according to claim 1, wherein each said vane has an internal portion contiguous with said external portion, said internal portions extending toward said opening.
 3. The diffuser according to claim 2, wherein said vanes are curvilinear and spaced apart from each other.
 4. The diffuser according to claim 2, wherein said internal portions terminate prior to reaching said opening so as to collectively form a collection chamber for the airflow.
 5. The diffuser according to claim 1, wherein each said vane has a plate edge at said motor side and ring edge opposite said plate edge.
 6. The diffuser according to claim 5, further comprising: a vane support ring connected to at least some of said vanes.
 7. The diffuser according to claim 6, wherein said vane support ring is connected to at least some of said ring edges, said vane support ring having an inner edge with a diameter at least equal to or larger than said baffle plate's diameter.
 8. The diffuser according to claim 1, wherein each said vane comprises a radial turning vane.
 9. The diffuser according to claim 1, wherein said baffle plate is annular.
 10. The diffuser according to claim 1, wherein said plurality of vanes total a number equal to a prime number.
 11. The diffuser according to claim 1, further comprising: at least one brush cap connected to said motor side of said baffle plate.
 12. A motor-fan assembly comprising: a field winding; an armature having a shaft, said armature rotatably mounted within said field winding; a fan attached to said shaft; and a diffuser interposed between said fan and said field winding, said diffuser comprising: a baffle plate having a motor side and a fan side; said baffle plate having an opening therethrough; a plurality of vanes extending from said motor side; each said vane having an external portion which radially extends from said baffle plate wherein adjacent vanes have a port therebetween; and said plurality of vanes directing airflow generated by the fan from said fan side through said ports to said motor side.
 13. The motor assembly according to claim 12, wherein each said vane has an internal portion contiguous with said external portion, said internal portion extending toward said opening.
 14. The motor assembly according to claim 13, wherein said vanes are curvilinear and spaced apart from each other.
 15. The motor assembly according to claim 13, wherein said internal portions terminate prior to reaching said opening so as to collectively form a collection chamber for the airflow.
 16. The motor assembly according to claim 12, wherein each said vane has a plate edge at said motor side and ring edge opposite said plate edge.
 17. The motor assembly according to claim 16, further comprising: a vane support ring connected to at least some of said vanes.
 18. The motor assembly according to claim 17, wherein said vane support ring is connected to at least some of said ring edges, said vane support ring having an inner edge with a diameter at least equal to or larger than said baffle plate's diameter.
 19. The motor assembly according to claim 12, wherein each said vane comprises a radial turning vane.
 20. The motor assembly according to claim 19, wherein said plurality of radial turning vanes total a number equal to a prime number.
 21. The motor assembly according to claim 12, wherein said baffle plate is annular.
 22. The motor assembly according to claim 12, wherein said plurality of vanes total a number equal to a prime number. 